Method of Lubricating an Internal Combustion Engine

ABSTRACT

The present invention relates to a method of lubricating an internal combustion engine with a power output of at least 1600 kilowatts by supplying to the internal combustion engine a lubricating composition containing an oil of lubricating viscosity and at least 0.5 wt % of a hydrocarbyl-substituted carboxylic acid or anhydride thereof. The invention further provides a lubricating composition suitable for the method.

FIELD OF INVENTION

The present invention relates to a method of lubricating an internalcombustion engine with a power output of at least 1600 kilowatts with alubricating composition comprising (a) an oil of lubricating viscosityand (b) at least 0.5 wt % of a hydrocarbyl-substituted carboxylic acidor anhydride thereof. The invention further provides a lubricatingcomposition suitable for the method.

BACKGROUND OF THE INVENTION

Lubricant compositions are known to provide a lubricating oil filmbetween different components within an internal combustion engine. Thelubricating oil film is known to help provide protection to improveoxidative and thermal stability, to help reduce corrosive and adhesivewear. In addition the lubricant compositions help impart cleanliness tothe engine. One of the important features that lubricants have that helpin protecting the engine is the lubricating oil film “thickness,” i.e.,viscosity. However, for a lubricant to perform at an optimum level, theoil film thickness has to provide a balance between being thin enough tospread efficiently over a surface but yet thick enough to provide acontinuous film that does not readily evaporate when exposed to engineoperating temperatures.

Control of lubricant thickness has been achieved by employing a widevariety of polymeric viscosity modifiers and/or bright stock. Polymericviscosity modifiers include, for example, polymethacrylates, polyolefinsand polyisobutylenes. International Publication WO 99/64543, forexample, discloses diesel cylinder oil having a viscosity index of atleast 95 and a total base number of at least 40 mg KOH/g. The oilfurther contains 1 wt % to 20 wt % of a liquid polyisobutylene having aviscosity from 1500 to 8000 mm²/s at 100° C. However, viscositymodifiers are believed to increase piston deposit levels.

Bright Stock is a lubricating oil component of high viscosity typicallyobtained from residues of petroleum distillation. Bright stock has beenutilized in many lubricants, particularly those requiring SAE 40 or SAE50 (16.3 mm²/s to 21.9 mm²/s) viscosities, bright stock is believed toprovide a lubricant with reduced oxidative or thermal stability.However, the availability of bright stock is diminishing, resulting inhigh volume uses such as those for 2-stroke or 4-stroke marine orstationary power engines requiring alternative solutions to impart thedesired viscometrics in lubricants.

The present invention solves the problem of providing an internalcombustion engine with a lubricating composition, especially 2-stroke or4-stroke marine or stationary power engines capable of providing atleast one property from control of viscometrics, acceptable depositaccumulation, acceptable oxidative stability and a partial or completereplacement for current viscosity modifiers or bright stock.

SUMMARY OF THE INVENTION

In one embodiment the invention provides a method of lubricating aninternal combustion engine with a power output of at least 1600kilowatts, comprising supplying to the internal combustion engine alubricating composition comprising (a) an oil of lubricating viscosityand (b) at least 0.5 wt % of a carboxylic acid having a hydrocarbylgroup of at least 10, or at least 30 carbon atoms or an anhydridethereof.

In one embodiment the invention provides a method of lubricating a2-stroke internal combustion engine comprising supplying to the internalcombustion engine a lubricating composition comprising (a) an oil oflubricating viscosity and (b) at least 0.5 wt % of a carboxylic acidhaving a hydrocarbyl group of at least 10, or at least 30 carbon atomsor an anhydride thereof.

In one embodiment the invention provides a method of lubricating amarine-diesel internal combustion engine comprising supplying to theinternal combustion engine a lubricating composition comprising (a) anoil of lubricating viscosity and (b) at least 0.5 wt % of a carboxylicacid having a hydrocarbyl group of at least 10, or at least 30 carbonatoms or an anhydride thereof.

In one embodiment the invention provides a lubricating compositioncomprising (a) an oil of lubricating viscosity, (b) at least 0.5 wt % ofa carboxylic acid having a hydrocarbyl group of at least 10, or at least30 carbon atoms or an anhydride thereof, and (c) at least 5 wt % of anoverbased sulphonate detergent.

In another embodiment the invention provides the use of a carboxylicacid having a hydrocarbyl group of at least 10, or at least 30 carbonatoms or an anhydride thereof as an oil thickener for a lubricatingcomposition, wherein the carboxylic acid or anhydride thereof is presentat least 0.5 wt % of the lubricating composition.

In another embodiment the invention provides the use of a carboxylicacid having a hydrocarbyl group of at least 10, or at least 30 carbonatoms or an anhydride thereof as an oil thickener for a 2-stroke marinediesel cylinder lubricating composition, wherein the carboxylic acid oranhydride thereof is present at least 0.5 wt % of the lubricatingcomposition.

The carboxylic acid as defined above may be written as “at least 0.5 wt% of a carboxylic acid or an anhydride thereof, wherein the carboxylicacid or anhydride thereof has a hydrocarbyl group of at least about 10carbon atoms”.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a method of lubricating an internalcombustion engine and a lubricating composition as disclosed above.

As used herein the term “substantially free of, to free of” means thatthe substance in question (e.g, the bright stock or dispersant) may bepresent from 0 wt % to 1 wt % of the lubricating composition.

In one embodiment the method employs a lubricating composition that maybe substantially reduced (e.g., 0 to less than 15 wt %, or 0.1 to 10 wt%) compared with conventional amounts (typically 15 to 40 wt % of alubricating composition) in amount of bright stock. In one embodimentthe lubricating composition may be substantially free of, to free ofbright stock.

In one embodiment method employs a lubricating composition that may besubstantially reduced (e.g., 0 to less than 3 wt %, or 0 to 2 wt %)compared with conventional amounts (typically 2 to 5 wt % of alubricating composition) in amount of dispersant

In one embodiment the method employs a lubricating composition that maycontain 0 to less than 15 wt %, or 0.1 to 10 wt % of bright stock; and 0to less than 3 wt %, or 0 to 2 wt % of a dispersant.

In one embodiment method employs a lubricating composition that may besubstantially free of, to free of both bright stock and dispersant.

Hydrocarbyl-Substituted Carboxylic Acid or Anhydride

The lubricant of the invention further comprises a carboxylic acid or ananhydride thereof, wherein the carboxylic acid or anhydride thereof hasa hydrocarbyl group of at least about 10 carbon atoms, or mixturesthereof. Hereinafter, this acid is sometimes referred to simply as ahydrocarbyl-substituted carboxylic acid, or even as the carboxylic acid.If the hydrocarbyl group containing 10 carbon atoms is attached to asimple mono-carboxylic group, there will accordingly be 11 carbon atomsin the molecule. If the hydrocarbyl group containing 10 carbon atoms isattached to, for instance, succinic acid, there will accordingly be 14carbon atoms in the molecule. A hydrocarbyl group containing 10 carbonatoms will normally have a molecular weight of about 141, varyingdepending on the presence of unsaturation, cyclic structures, heterogroups, or other substituents, if any.

The carboxylic acid or anhydride thereof may be substituted by orderived from a polyolefin. The polyolefin may be a homopolymer,copolymer, or interpolymer. The polyolefin may be prepared frompolymerisable monomers containing 2 to 16, or 2 to 8, or 2 to 6 carbonatoms. Often the polymerisable monomers comprise one or more ofpropylene, isobutene, 1-butene, isoprene, 1,3-butadiene, or mixturesthereof.

In one embodiment the carboxylic acid or anhydride thereof comprises asuccinic acid or anhydride thereof.

In one embodiment the hydrocarbyl-substituted carboxylic acid oranhydride thereof comprises a polyisobutylene succinic acid or anhydridethereof. A more detailed description of a suitable carboxylic acid oranhydride thereof is described in WO 93/03121, page 33, line 10 to page37, line 20.

In view of the synthesis routes commercially employed to prepare thehydrocarbyl-substituted carboxylic acid or anhydride thereof, there maybe a portion of unreacted hydrocarbyl group (typically polyisobutylene)present. The amount of the unreacted hydrocarbyl group may as high asabout 25 wt %, or as low as 0 wt % of the hydrocarbyl-substitutedcarboxylic acid or anhydride thereof.

The hydrocarbyl-substituted carboxylic acid or anhydride thereof may bepresent at 0.5 to 20 wt % or 1 to 10 wt % of the lubricatingcomposition.

Typically the hydrocarbyl-substituted carboxylic acid or anhydridethereof is a polyisobutylene succinic acid or anhydride.

The hydrocarbyl group of the carboxylic acid or anhydride thereof maytypically contain 10 to 400, or 20 to 200, or 30 to 200, or 40 to 150carbon atoms.

The hydrocarbyl group of the hydrocarbyl-substituted carboxylic acid oranhydride thereof may have a number average molecular weight of 450 to20,000, or 550 to 10,000, or 750 to 5000, or 1500 to 3000.

In one embodiment the hydrocarbyl group of the hydrocarbyl-substitutedcarboxylic acid or anhydride thereof may have number average molecularweight of 450 to 1500. The acid or anhydride having such a group may, inone embodiment, be present at 2 to 20 wt % or 4 to 10 wt % of thelubricating composition.

In one embodiment the hydrocarbyl group of the hydrocarbyl-substitutedcarboxylic acid or anhydride thereof may have a number average molecularweight of greater than 1500 to 5000. The acid or anhydride having such agroup may, in one embodiment, be present at 0.5 to less than 10 wt % or1 to 5 wt % of the lubricating composition.

Detergent

In one embodiment the lubricating composition further comprises at leastone detergent selected from the group consisting of sulphonates,salicylates, salixarates, phenates and hybrid detergent, such assulphonate-phenate compositions, phenate-salicylate compositions orphenate-stearate compositions.

The total amount of detergent in the lubricating composition may be 0 wt% to 50 wt %, or at least 5 wt % to 35 wt %, or 6.5 wt % to 32 wt %, or9 wt % to 30 wt %, or 12 wt % to 28 wt % of the lubricating composition.

In one embodiment the detergent may be an overbased sulphonatedetergent.

The sulphonate detergent of the composition includes compoundsrepresented by the formula:

(R¹)_(k)-A-SO₃M  (I)

wherein each R¹ may be a hydrocarbyl group, typically each hydrocarbylgroup may contain 6 to 40, or 8 to 35 or 12 to 30 carbon atoms; A may beindependently a cyclic or acyclic divalent hydrocarbon group; M may behydrogen, a valence of a metal ion, an ammonium ion or mixtures thereof;and k may be an integer of 0 to 5, for example 0, 1, 2, 3, 4, 5. In oneembodiment k may be 1, 2 or 3, or 1 or 2. In one embodiment M may behydrogen and typically present on less than 30%, or less than 20%, orless than 10% or less than 5% of the available M entities, the balanceof the M entities being a metal or ammonium ion.

In one embodiment k is 1 and R¹ may be a branched alkyl group with 6 to40 carbon atoms. In one embodiment k may be 1 and R¹ is a linear alkylgroup with 6 to 40 carbon atoms.

Examples of suitable sulphonic acids capable of forming the overbasedsulphonate detergent include polypropene benzene sulphonic acid, undecylbenzene sulphonic acid, dodecyl benzene sulphonic acid, tridecyl benzenesulphonic acid, tetradecyl benzene sulphonic acid, pentadecyl benzenesulphonic acid, hexadecyl benzene sulphonic acid and mixtures thereof.In one embodiment the sulphonic acid includes tridecyl benzene sulphonicacid, tetradecyl benzene sulphonic acid, octadecyl benzene sulphonicacid, tetraeicosyl benzene sulphonic acid or mixtures thereof. In oneembodiment of the invention the sulphonic acid is a polypropene benzenesulphonic acid, where the polypropene contains 18 to 30 carbon atoms.

In one embodiment of the invention the sulphonate components may becalcium polypropene benzenesulphonate and calcium monoalkyl and dialkylbenzenesulphonates wherein the alkyl groups contain at least 10 or 12carbons, for example 11, 12, 13, 14, 15, 18, 24 or 30 carbon atoms.

When M is a valence of a metal ion, the metal may be monovalent,divalent, trivalent or mixtures of such metals. When monovalent, themetal M includes an alkali metal such as lithium, sodium, or potassiumand when divalent, the metal M includes an alkaline earth metal such asmagnesium, calcium or barium. In one embodiment the metal may be analkaline earth metal. In one embodiment the metal is calcium.

When A is cyclic hydrocarbon group, suitable groups include phenylene orfused bicyclic groups such as naphthylene, indenylene, indanylene,bicyclopentadienylene or mixtures thereof. In one embodiment A comprisesa benzene ring.

When A is an acyclic divalent hydrocarbon group, the carbon chain may belinear or branched. In one embodiment A may be an acyclic linearhydrocarbon group.

The overbased sulphonate detergent in one embodiment has a TBN (totalbase number) of at least 350, or at least 400, or at least 425, or atleast 450, or at least 475. In one embodiment the overbased sulphonatedetergent has a TBN of between 400 and 500.

A sulphonate detergent with 500 TBN and its preparation are disclosed inU.S. Pat. No. 5,792,732. In Example 2 thereof, a 500 TBN all-linearalkylbenzene sulphonate is prepared by reacting an alkyl benzenesulphonate from Witco Corp. (now known as Chemtura) with Ca(OH)₂ and CaOin n-heptane and methanol and bubbling with CO₂. It is also reported inthe aforementioned patent (col. 5) that a 500 TBN overbased sulphonatecontaining highly branched alkylbenzene sulphonate is available fromWitco Corp. (now known as Chemtura) as Petronate® C-500. Another methodfor preparing an overbased sulphonate detergent of high metal ratio isdisclosed in U.S. Pat. No. 6,444,625 (see, for instance, column 3,bottom).

Optionally the lubricating composition further includes a phenatedetergent. The phenate detergent is known and includes neutral andoverbased metal salts of a sulphur-containing phenate, a non-sulphurisedphenate or mixtures thereof. Suitable metal salts are the same as thosedescribed for the sulphonate detergent.

The phenate detergent in one embodiment has a TBN from 30 to 450, inanother embodiment 30 to 350 or 290, in another embodiment 40 to 265, inanother embodiment 50 to 190 and in another embodiment 70 to 175. In oneembodiment the sulphur containing phenate detergent has a TBN of 150, inanother embodiment a TBN of 225 and in another embodiment 250.

The detergent may also be a hybrid (or complex) detergent.

In one embodiment the complex/hybrid may be an overbasedphenate-stearate detergent, typically with a TBN of 300 to 450. Methodsof preparing overbased phenate-stearate detergents are disclosed in EP271262 B1 and EP273 588 B1.

In one embodiment the complex/hybrid may be an overbasedphenate-salicylate detergent. Methods of preparing overbasedphenate-salicylate detergents are disclosed in EP 123 6791 A1 and EP 1236792 A1.

In one embodiment the complex/hybrid may be prepared by reacting, in thepresence of the suspension and acidifying overbasing agent, alkylaromatic sulphonic acid and at least one alkyl phenol (such as, alkylphenol, aldehyde-coupled alkyl phenol, sulphurised alkyl phenol) andoptionally alkyl salicylic acid.

A hybrid detergent may be prepared by hybrid preparing an overbasedcalcium detergent composed of a sulphonic acid and an alkyl phenol. Ahybrid detergent may be prepared as disclosed in WO97046643 or by thefollowing preparative Example.

Preparative Example 1

540 g of toluene, 276 g of methanol and 290 g of the product of lime aremixed at ambient temperature in a vessel. Then 238 g of sulphurisedalkyl phenol and 110 g of alkyl sulphonic acid (with molecular weight of683) are charged along with 22 g of water and an additional 50 g oftoluene at 40° C. After neutralization the vessel is cooled to 28° C.while 62 g of carbon dioxide is injected. The reaction temperature isincreased to 60° C. over a period of 1 hour, before cooling to 28° C.254 g of lime is added and a second carbonation step carried out, whilstheating to 60° C. over 90 minutes. The product of the reaction is cooledand filtered.

Oils of Lubricating Viscosity

The invention further includes oil of lubricating viscosity. The oil oflubricating viscosity may have a SAE grade of SAE 30, SAE 40, SAE 50, orSAE 60. In one embodiment the oil of lubricating viscosity may be a SAE50 oil. Typically a SAE 50 oil has a kinematic viscosity of 16.3 mm²/sto 21.9 mm²/s at 100° C.

Such oils include natural and synthetic oils, oil derived fromhydrocracking, hydrogenation, and hydrofinishing, unrefined, refined andre-refined oils and mixtures thereof.

Unrefined oils are those obtained directly from a natural or syntheticsource generally without (or with little) further purificationtreatment.

Refined oils are similar to the unrefined oils except they have beenfurther treated in one or more purification steps to improve one or moreproperties. Purification techniques are known in the art and includesolvent extraction, secondary distillation, acid or base extraction,filtration, percolation and the like.

Re-refined oils are also known as reclaimed or reprocessed oils, and areobtained by processes similar to those used to obtain refined oils andoften are additionally processed by techniques directed to removal ofspent additives and oil breakdown products.

Natural oils useful in making the inventive lubricants include animaloils, vegetable oils (e.g., castor oil, lard oil), mineral lubricatingoils such as liquid petroleum oils and solvent-treated or acid-treatedmineral lubricating oils of the paraffinic, naphthenic or mixedparaffinic-naphthenic types and oils derived from coal or shale ormixtures thereof.

Synthetic lubricating oils are useful and include hydrocarbon oils suchas polymerised and interpolymerised olefins (e.g., polybutylenes,polypropylenes, propyleneisobutylene copolymers); poly(1-hexenes),poly(1-octenes), poly(1-decenes), and mixtures thereof; alkyl-benzenes(e.g. dodecylbenzenes, tetradecylbenzenes, dinonylbenzenes,di-(2-ethylhexyl)-benzenes); polyphenyls (e.g., biphenyls, terphenyls,alkylated polyphenyls); alkylated diphenyl ethers and alkylated diphenylsulphides and the derivatives, analogs and homologs thereof or mixturesthereof.

Other synthetic lubricating oils include but are not limited to liquidesters of phosphorus-containing acids (e.g., tricresyl phosphate,trioctyl phosphate, and the diethyl ester of decane phosphonic acid),and polymeric tetrahydrofurans. Synthetic oils may be produced byFischer-Tropsch reactions and typically may be hydroisomerisedFischer-Tropsch hydrocarbons or waxes.

Oils of lubricating viscosity may also be defined as specified in theAmerican Petroleum Institute (API) Base Oil InterchangeabilityGuidelines. The five base oil groups are as follows: Group I (sulphurcontent>0.03 wt %, and/or <90 wt % saturates, viscosity index 80-120);Group II (sulphur content≦0.03 wt %, and ≧90 wt % saturates, viscosityindex 80-120); Group III (sulphur content≦0.03 wt %, and ≧90 wt %saturates, viscosity index≧120); Group IV (all polyalphaolefins (PAOs));and Group V (all others not included in Groups I, II, III, or IV). Theoil of lubricating viscosity comprises an API Group I, Group II, GroupIII, Group IV, Group V oil and mixtures thereof. Often the oil oflubricating viscosity is an API Group I, Group II, Group III, Group IVoil and mixtures thereof. Alternatively the oil of lubricating viscosityis often an API Group I, Group II, Group III oil or mixtures thereof.

Other Performance Additives

The lubricating composition optionally contains at least one otherperformance additive. Typically the other performance additives includemetal deactivators, dispersant, antioxidants, antiwear agents, corrosioninhibitors, antiscuffing agents, extreme pressure agents, foaminhibitors, demulsifiers, friction modifiers, viscosity modifiers, pourpoint depressants and mixtures thereof. Typically, fully-formulatedlubricating oil will contain one or more of these performance additives.

Dispersants

Dispersants are often known as ashless-type dispersants because, priorto mixing in a lubricating oil composition, they do not containash-forming metals and they do not normally contribute any ash formingmetals when added to a lubricant and polymeric dispersants. Ashless typedispersants are characterised by a polar group attached to a relativelyhigh molecular weight hydrocarbon chain. Typical ashless dispersantsinclude N-substituted long chain alkenyl succinimides. Examples ofN-substituted long chain alkenyl succinimides include polyisobutylenesuccinimide with number average molecular weight of the polyisobutylenesubstituent in the range 350 to 5000, or 500 to 3000. Succinimidedispersants and their preparation are disclosed, for instance in U.S.Pat. No. 3,172,892 or U.S. Pat. No. 4,234,435. Succinimide dispersantsare typically the imide formed from a polyamine, typically apoly(ethyleneamine).

In one embodiment the invention further comprises at least onedispersant derived from polyisobutylene succinimide with number averagemolecular weight in the range 350 to 5000, or 500 to 3000. Thepolyisobutylene succinimide may be used alone or in combination withother dispersants.

In one embodiment the invention further comprises at least onedispersant derived from polyisobutylene succinic anhydride, an amine andzinc oxide to form a polyisobutylene succinimide complex with zinc. Thepolyisobutylene succinimide complex with zinc may be used alone or incombination.

Another class of ashless dispersant is Mannich bases. Mannichdispersants are the reaction products of alkyl phenols with aldehydes(especially formaldehyde) and amines (especially polyalkylenepolyamines). The alkyl group typically contains at least 30 carbonatoms.

The dispersants may also be post-treated by conventional methods by areaction with any of a variety of agents. Among these are boron, urea,thiourea, dimercaptothiadiazoles, carbon disulphide, aldehydes, ketones,carboxylic acids, hydrocarbon-substituted succinic anhydrides, maleicanhydride, nitriles, epoxides, and phosphorus compounds.

The dispersant may be present from 0 wt % to 5 wt %, or 0 wt % to 3 wt%, or 0 wt % to 2 wt %, or 0.1 wt % to 2 wt %.

Antioxidants

Antioxidant compounds are known and include for example, sulphurisedolefins, alkylated diphenylamines (typically di-nonyl diphenylamine,octyl diphenylamine, di-octyl diphenylamine), hindered phenols,molybdenum compounds (such as molybdenum dithiocarbamates), or mixturesthereof. Antioxidant compounds may be used alone or in combination.

The hindered phenol antioxidant often contains a secondary butyl and/ora tertiary butyl group as a sterically hindering group. The phenol groupis often further substituted with a hydrocarbyl group and/or a bridginggroup linking to a second aromatic group. Examples of suitable hinderedphenol antioxidants include 2,6-di-tert-butylphenol,4-methyl-2,6-di-tert-butylphenol, 4-ethyl-2,6-di-tert-butylphenol,4-propyl-2,6-di-tert-butylphenol or 4-butyl-2,6-di-tert-butylphenol, or4-dodecyl-2,6-di-tert-butylphenol. In one embodiment the hindered phenolantioxidant is an ester and may include, e.g., Irganox™ L-135 from Ciba.A more detailed description of suitable ester-containing hindered phenolantioxidant chemistry is found in U.S. Pat. No. 6,559,105.

Suitable examples of molybdenum dithiocarbamates which may be used as anantioxidant include commercial materials sold under the trade names suchas Molyvan 822™ and Molyvan™ A from R. T. Vanderbilt Co., Ltd., andAdeka Sakura-Lube™ S-100, S-165 and S-600 from Asahi Denka Kogyo K. Kand mixtures thereof.

Viscosity Modifiers

Viscosity modifiers include hydrogenated copolymers of styrene andbutadiene, ethylene-propylene copolymers, polyisobutenes, hydrogenatedstyrene-isoprene polymers, hydrogenated isoprene polymers,polymethacrylates, polyacrylates, polyalkyl styrenes, hydrogenatedalkenyl aryl conjugated diene copolymers, polyolefins, esters of maleicanhydride-styrene copolymers.

Antiwear Agents

The lubricant composition optionally further comprises at least oneantiwear agent (other than the various other components mentioned hereinthat may also impart some antiwar functionality). The antiwear agent maybe present in ranges including 0 wt % to 15 wt %, or 0.1 wt % to 10 wt %or 1 wt % to 8 wt % of the lubricating composition. Examples of suitableantiwear agents include a boron-containing compound such as borateesters or borate alcohols, phosphate esters, sulphurised olefins,sulphur-containing ashless anti-wear additives are metaldihydrocarbyldithiophosphates (such as zinc dialkyldithiophosphates ormolybdenum dialkyldithiophosphates), thiocarbamate-containing compounds,such as thiocarbamate esters, alkylene-coupled thiocarbamates, andbis-(S-alkyldithiocarbamyl)disulphides.

The borate esters or borate alcohols may be substantially the sameexcept the borate alcohol has at least one hydroxyl group that is notesterified. Therefore, as used herein the term “borate ester” is used torefer to either borate ester or borate alcohol. The borate esters orborate alcohols may have a formula B(OR′)₃ or be a derivative thereofcontaining a >B—O—B< group, wherein R′ may be hydrogen or a hydrocarbylgroup, typically containing 1 to 40, or 1 to 20 carbon atoms on each R′.When R′ is hydrogen, the boron-containing compound is a borate alcohol.When R′ is hydrogen, the boron-containing compound is a borate alcohol.When R′ is hydrocarbyl, the boron-containing compound is a borate ester.

The borate ester may be prepared by the reaction of a boron compound andat least one compound selected from epoxy compounds, halohydrincompounds, epihalohydrin compounds, alcohols and mixtures thereof. Thealcohols include dihydric alcohols, trihydric alcohols or higheralcohols, with the proviso for one embodiment that hydroxyl groups areon adjacent carbon atoms i.e. vicinal.

The borate ester may be prepared by blending the boron compound and theepoxy compounds or alcohols described above and heating them at asuitable temperature, such as at 80° C. to 250° C., 90° C. to 240° C.,or 100° C. to 230° C., until the desired reaction has occurred. Themolar ratio of the boron compounds to the epoxy compounds is typically4:1 to 1:4, or 1:1 to 1:3, or 1:2. An inert liquid may be used inperforming the reaction. The liquid may be, for instance, toluene,xylene, chlorobenzene, dimethylformamide and mixtures thereof. Water istypically formed and is distilled off during the reaction. Alkalinereagents may be used to catalyze the reaction.

Boron compounds suitable for preparing the borate ester include thevarious forms selected from the group consisting of boric acid(including metaboric acid, HBO₂, orthoboric acid, H₃BO₃, and tetraboricacid, H₂B₄O₇), boric oxide, boron trioxide and alkyl borates. The borateester may also be prepared from boron halides.

In one embodiment suitable borate ester compounds include tripropylborate, tributyl borate, tripentyl borate, trihexyl borate, triheptylborate, trioctyl borate, trinonyl borate and tridecyl borate.

The dithiocarbamate-containing compounds may be prepared by reacting adithiocarbamate acid or salt with an unsaturated compound. Thedithiocarbamate containing compounds may also be prepared bysimultaneously reacting an amine, carbon disulphide and an unsaturatedcompound. Generally, the reaction occurs at a temperature of 25° C. to125° C. U.S. Pat. Nos. 4,758,362 and 4,997,969 describe dithiocarbamatecompounds and methods of making them.

Examples of suitable olefins that may be sulphurised to form an thesulphurised olefin include propylene, butylene, isobutylene, pentene,hexane, heptene, octane, nonene, decene, undecene, dodecene, undecyl,tridecene, tetradecene, pentadecene, hexadecene, heptadecene,octadecene, octadecenene, nonodecene, eicosene or mixtures thereof. Inone embodiment, hexadecene, heptadecene, octadecene, octadecenene,nonodecene, eicosene or mixtures thereof and their dimers, trimers andtetramers are especially useful olefins. Alternatively, the olefin maybe a Diels-Alder adduct of a diene such as 1,3-butadiene and anunsaturated ester, such as, butylacrylate.

Another class of sulphurised olefin includes fatty acids and theiresters. The fatty acids are often obtained from vegetable oil or animaloil and typically contain 4 to 22 carbon atoms. Examples of suitablefatty acids and their esters include triglycerides, oleic acid, linoleicacid, palmitoleic acid or mixtures thereof. Often, the fatty acids areobtained from lard oil, tall oil, peanut oil, soybean oil, cottonseedoil, sunflower seed oil or mixtures thereof. In one embodiment fattyacids and/or ester are mixed with olefins.

In an alternative embodiment, the ashless antiwear agent (which may alsobe described as a friction modifier) may be a monoester of a polyol andan aliphatic carboxylic acid, often an acid containing 12 to 24 carbonatoms. Often the monoester of a polyol and an aliphatic carboxylic acidis in the form of a mixture with a sunflower oil or the like, which maybe present in the ashless antiwear agent mixture include 5 to 95, or inother embodiments 10 to 90, or 20 to 85, or 20 to 80 weight percent ofsaid mixture. The aliphatic carboxylic acids (especially amonocarboxylic acid) which form the esters are those acids typicallycontaining 12 to 24 or 14 to 20 carbon atoms. Examples of carboxylicacids include dodecanoic acid, stearic acid, lauric acid, behenic acid,and oleic acid.

Polyols include diols, triols, and alcohols with higher numbers ofalcoholic OH groups. Polyhydric alcohols include ethylene glycols,including di-, tri- and tetraethylene glycols; propylene glycols,including di-, tri- and tetrapropylene glycols; glycerol; butane diol;hexane diol; sorbitol; arabitol; mannitol; sucrose; fructose; glucose;cyclohexane diol; erythritol; and pentaerythritols, including di- andtripentaerythritol. Often the polyol is diethylene glycol, triethyleneglycol, glycerol, sorbitol, pentaerythritol or dipentaerythritol.

The commercially available monoester known as “glycerol monooleate” isbelieved to include 60±5 percent by weight of the chemical speciesglycerol monooleate, along with 35±5 percent glycerol dioleate, and lessthan 5 percent trioleate and oleic acid. The amounts of the monoesters,described above, are calculated based on the actual, corrected, amountof polyol monoester present in any such mixture.

Extreme Pressure Agents

Extreme Pressure (EP) agents that are soluble in the oil includesulphur- and chlorosulphur-containing EP agents, chlorinated hydrocarbonEP agents and phosphorus EP agents. Examples of such EP agents includechlorinated wax; organic sulphides and polysulphides such asdibenzyldisulphide, bis-(chlorobenzyl)disulphide, dibutyl tetrasulphide,sulphurised methyl ester of oleic acid, sulphurised alkylphenol,sulphurised dipentene, sulphurised terpene, and sulphurised Diels-Alderadducts; phosphosulphurised hydrocarbons such as the reaction product ofphosphorus sulphide with turpentine or methyl oleate; phosphorus esterssuch as the dihydrocarbon and trihydrocarbon phosphites, e.g., dibutylphosphite, diheptyl phosphite, dicyclohexyl phosphite, pentylphenylphosphite; dipentylphenyl phosphite, tridecyl phosphite, distearylphosphite and polypropylene substituted phenol phosphite; metalthiocarbamates such as zinc dioctyldithiocarbamate and bariumheptylphenol diacid; amine salts of alkyl and dialkylphosphoric acids,including, for example, the amine salt of the reaction product of adialkyldithiophosphoric acid with propylene oxide; and mixtures thereof.

Other performance additives such as corrosion inhibitors include thosedescribed in paragraphs 5 to 8 of U.S. application Ser. No. 05/038,319(filed on Oct. 25, 2004 McAtee and Boyer as named inventors), octylamineoctanoate, condensation products of dodecenyl succinic acid or anhydrideand a fatty acid such as oleic acid with a polyamine. In one embodimentthe corrosion inhibitors include the Synalox® corrosion inhibitor. TheSynalox® corrosion inhibitor is typically a homopolymer or copolymer ofpropylene oxide. The Synalox® corrosion inhibitor is described in moredetail in a product brochure with Form No. 118-01453-0702 AMS, publishedby The Dow Chemical Company. The product brochure is entitled “SYNALOXLubricants, High-Performance Polyglycols for Demanding Applications.”

Metal deactivators including derivatives of benzotriazoles (typicallytolyltriazole), dimercaptothiadiazole derivatives, 1,2,4-triazoles,benzimidazoles, 2-alkyldithiobenzimidazoles, or2-alkyldithiobenzothiazoles; foam inhibitors including copolymers ofethyl acrylate and 2-ethylhexylacrylate and optionally vinyl acetate;demulsifiers including trialkyl phosphates, polyethylene glycols,polyethylene oxides, polypropylene oxides and (ethylene oxide-propyleneoxide) polymers; pour point depressants including esters of maleicanhydride-styrene, polymethacrylates, polyacrylates or polyacrylamides.

Friction modifiers including fatty acid derivatives such as amines,esters, epoxides, fatty imidazolines, condensation products ofcarboxylic acids and polyalkylene-polyamines and amine salts ofalkylphosphoric acids, fatty alkyl tartrates, fatty alkyl tartrimides,fatty alkyl tartramides may also be used in the lubricant composition.Friction modifiers may also encompass materials such as sulphurisedfatty compounds and olefins, molybdenum dialkyldithiophosphates,molybdenum dithiocarbamates, sunflower oil or monoester of a polyol andan aliphatic carboxylic acid (all these friction modifiers have beendescribed above as antioxidants or antiwear agents).

INDUSTRIAL APPLICATION

The method and lubricating composition of the invention may be suitablefor 2-stroke or 4-stroke internal combustion engines. Typically the2-stroke engine may be a 2-stroke cross-head engine.

The power output of the engine may be at least 2000 kilowatts, or atleast 3000 kilowatts, or at least 4700 kilowatts.

The 2-stroke internal combustion engine may be a marine diesel engine ora stationary power engine.

In one embodiment the engine may be marine-diesel internal combustionengine is a 2-stroke engine.

In one embodiment the 2-stroke engine employs the lubricatingcomposition in a cylinder liner.

EXAMPLES Marine Diesel Cylinder Lubricants Invention and ReferenceLubricating Oil Compositions

Lubricating oil compositions are prepared as summarised in Table 1below. The amounts of sulphonate, phenate and dispersant quoted includethe normal amounts of diluent oil associated with additives. Typicallythe sulphonate, phenate and dispersant contain about 40 wt % of diluentoil.

Reference oil composition 1 (RF1) is a lubricant containing bright stock(150 BS) and dispersant. Reference oil compositions 2 (RF2) and 3 (RF3)contain polyisobutylene as a thickener, no bright stock. The lubricatingoil compositions of the invention 1 (LC1) and 2 (LC2) containpolyisobutylene succinic anhydride, no dispersant and no bright stock.

TABLE 1 RF1 RF2 RF3 LC1 LC2 Formulation Components wt % Formulated toKinematic Viscosity 19.8 19.4 19.5 19.4 19.5 at 100° C. (ASTM D445)mm²/s 400 TBN sulphonate 10.6 10.6 10.6 10.6 10.6 255 TBN phenate 10.610.6 10.6 10.6 10.6 Dispersant 2 0 0 0 0 Polyisobutylene with Mn of 09.5 0 0 0 approximately 950-1,000 Polyisobutylene with Mn of 0 0 5.2 0 0approximately 2,200-2,300 Polyisobutylene succinic anhydride 0 0 0 5 0derived from Polyisobutylene with Mn of approximately 950-1,000Polyisobutylene succinic anhydride 0 0 0 0 2.3 derived fromPolyisobutylene with Mn of approximately 2,200-2,300 Esso 600N base oil57.8 69.3 73.6 73.8 76.5 Esso 150BS bright stock 19 0 0 0 0

Test 1 Panel Coker:

Approximately 233 g of sample is placed in a 250 ml Panel Cokerapparatus and heated to 325° C. The sample is splashed against a metalplate for 15 seconds and then baked for 45 seconds. The splashing andbaking cycle is continued for approximately 3 hours. The sample iscooled to room temperature and the amount of deposits left on the metalplate is weighed. In addition the deposits are analysed using imageanalysis techniques. The image analysis techniques have a rating scalefrom 0 to 100, 0 indicating heavy deposits and 100 indicating no or verylittle deposits. The results are shown in Table 2.

Test 2 Hot Tube:

The reference and lubricating compositions and house air are fed atcontrolled rates through a heated Pyrex® glass capillary tube. The oiland air are brought together via a Pyrex® glass tee that is connected tothe bottom of the capillary tube. As the oil is metered into the glasstee, the air picks up the oil and carries it up through the verticalglass capillary tube which passes through an electrically heated andtemperature controlled aluminum block. The heated oil and air mixturethen exits from the top of the glass capillary into a collecting beakerfor the oxidized oil. At test completion, the glass capillary tubes areremoved from the heating block then flushed with hydrocarbon solvent andrated for lacquer and carbon deposits, using reference standards. Arating scale from 0 to 100 is used and evaluated using standard imageanalysis techniques, 0 indicating heavy deposits and 100 indicating noor very little deposits. The results are shown in Table 2.

TABLE 2 RF1 RF2 RF3 LC1 LC2 Test 1: Deposit (mg) 229 244 238 94 161 Test1: Image Analysis Rating 49 51 63 62 65 Test 2: Image Analysis Rating 166 14 8 18

Overall the data indicates that lubricating composition comprising atleast 0.5 wt % of a hydrocarbyl-substituted carboxylic acid or anhydridethereof may be more suitable for the engine disclosed herein and capableof producing at least one of fewer deposits and having cleaner ratingsthan lubricating compositions that contain bright stock orpolyisobutylene thickeners, and optionally dispersant.

As used herein, the term “hydrocarbyl substituent” or “hydrocarbylgroup” is used in its ordinary sense, which is well-known to thoseskilled in the art. Specifically, it refers to a group having a carbonatom directly attached to the remainder of the molecule and havingpredominantly hydrocarbon character. Examples of hydrocarbyl groupsinclude:

(i) hydrocarbon substituents, that is, aliphatic (e.g., alkyl oralkenyl), alicyclic (e.g., cycloalkyl, cycloalkenyl) substituents, andaromatic-, aliphatic-, and alicyclic-substituted aromatic substituents,as well as cyclic substituents wherein the ring is completed throughanother portion of the molecule (e.g., two substituents together form aring);

(ii) substituted hydrocarbon substituents, that is, substituentscontaining non-hydrocarbon groups which, in the context of thisinvention, do not alter the predominantly hydrocarbon nature of thesubstituent (e.g., halo (especially chloro and fluoro), hydroxy, alkoxy,mercapto, alkylmercapto, nitro, nitroso, and sulphoxy);

(iii) hetero substituents, that is, substituents which, while having apredominantly hydrocarbon character, in the context of this invention,contain other than carbon in a ring or chain otherwise composed ofcarbon atoms. Heteroatoms include sulphur, oxygen, nitrogen, andencompass substituents as pyridyl, furyl, thienyl and imidazolyl. Ingeneral, no more than two, preferably no more than one, non-hydrocarbonsubstituent will be present for every ten carbon atoms in thehydrocarbyl group; typically, there will be no non-hydrocarbonsubstituents in the hydrocarbyl group.

It is known that some of the materials described above may interact inthe final formulation, so that the components of the final formulationmay be different from those that are initially added. The productsformed thereby, including the products formed upon employing lubricantcomposition of the present invention in its intended use, may not besusceptible of easy description. Nevertheless, all such modificationsand reaction products are included within the scope of the presentinvention; the present invention encompasses lubricant compositionprepared by admixing the components described above.

Each of the documents referred to above is incorporated herein byreference. Except in the Examples, or where otherwise explicitlyindicated, all numerical quantities in this description specifyingamounts of materials, reaction conditions, molecular weights, number ofcarbon atoms, and the like, are to be understood as modified by the word“about.” Unless otherwise indicated, each chemical or compositionreferred to herein should be interpreted as being a commercial gradematerial which may contain the isomers, by-products, derivatives, andother such materials which are normally understood to be present in thecommercial grade. However, the amount of each chemical component ispresented exclusive of any solvent or diluent oil, which may becustomarily present in the commercial material, unless otherwiseindicated. It is to be understood that the upper and lower amount,range, and ratio limits set forth herein may be independently combined.Similarly, the ranges and amounts for each element of the invention maybe used together with ranges or amounts for any of the other elements.

While the invention has been explained in relation to its preferredembodiments, it is to be understood that various modifications thereofwill become apparent to those skilled in the art upon reading thespecification. Therefore, it is to be understood that the inventiondisclosed herein is intended to cover such modifications as fall withinthe scope of the appended claims.

1. A method of lubricating a 2-stroke internal combustion enginecylinder liner comprising supplying to the internal combustion engine alubricating composition comprising (a) an oil of lubricating viscosityand (b) at least 0.5 wt % to 20 wt % of a carboxylic acid or ananhydride thereof, wherein the carboxylic acid or anhydride thereof hasa hydrocarbyl group of at least about 10 carbon atoms.
 2. The method ofclaim 1 wherein the hydrocarbyl group of the carboxylic acid oranhydride thereof has number average molecular weight of 450 to 20,000.3. The method of claim 1 wherein the hydrocarbyl group of the carboxylicacid or anhydride thereof has number average molecular weight of 450 to1500, and wherein the carboxylic acid or anhydride thereof is present at2 to 20 wt % of the lubricating composition.
 4. The method of claim 1wherein the hydrocarbyl group of the carboxylic acid or anhydridethereof has number average molecular weight of greater than 1500 to5000, and wherein the carboxylic acid or anhydride thereof is present at0.5 to less than 10 wt % of the lubricating composition.
 5. The methodof claim 1 wherein the carboxylic acid or anhydride thereof is apolyisobutylene-substituted succinic acid or anhydride.
 6. The method ofclaim 1 wherein the lubricating composition has a SAE 40 viscosity orSAE 50 viscosity.
 7. The method of claim 1 wherein the lubricatingcomposition has 0 to less than 15 wt % of bright stock.
 8. The method ofclaim 1 wherein the lubricating composition contains 0 to less than 3 wt% of a dispersant.
 9. The method of claim 1 wherein the lubricatingcomposition contains 0 to less than 15 wt % of bright stock; and 0 to 2wt % of a dispersant.
 10. The method of claim 1 wherein the lubricatingcomposition further comprises at least one detergent selected from thegroup consisting of sulphonates, salicylates, salixarates, phenates,hybrid salicylate-phenate compositions, hybrid phenate-stearatecompositions and hybrid sulphonate-phenate compositions.
 11. The methodof claim 1, wherein the 2-stroke internal combustion engine is a marinediesel engine or a stationary power engine.
 12. A method of lubricatinga 2-stroke internal combustion engine cylinder liner comprisingsupplying to the internal combustion engine a lubricating compositioncomprising (a) an oil of lubricating viscosity and (b) at least 0.5 wt %to 20 wt % of a carboxylic acid or an anhydride thereof, wherein thecarboxylic acid or anhydride thereof has a hydrocarbyl group of at leastabout 10 carbon atoms, and (c) at least 5 wt % of an overbasedsulphonate detergent.
 13. A method of reducing the amount of brightstock in a lubricating composition used in lubricating a 2-strokeinternal combustion engine cylinder liner, comprising supplying to theinternal combustion engine a lubricating composition comprising (a) anoil of lubricating viscosity and (b) at least 0.5 wt % to 20 wt % of acarboxylic acid or an anhydride thereof, wherein the carboxylic acid oranhydride thereof has a hydrocarbyl group of at least about 10 carbonatoms.